Chalcogenide waveguides on a sapphire substrate for mid-IR applications

We report on the fabrication of arsenic tri-sulfide chalcogenide strip waveguides on a sapphire substrate, suitable for guiding 0.55-5 μm wavelengths. Propagation losses measured using the Fabry-Perot resonator technique are 2.78 dB/cm. The chalcogenide layer refractive index dispersion is evaluated by measuring the transmission as a function of wavelength prior to waveguide fabrication. Numerical simulations are used to compare between silica and sapphire substrates for mid-IR transmittance and to calculate the waveguide's effective refractive index in a suggested design. The use of a low-loss sapphire substrate redefines the mid-IR boundaries of chalcogenide waveguides for linear and nonlinear applications.